Purification of "inhibin" from human ovarian follicular fluid

Following the earlier demonstration of inhibin-like activity in human ovarian follicular fluid a method for its purification to apparent homogeneity is described. The fluid was converted to acetone powder and subjected sequentially to ammonium sulphate fractionation, gel chromatography on Sephadex G-200, continuous gradient ion-exchange chromatography on DEAE-cellulose, first with a pH gradient from 8.0 to 4.0 and then with a NaCl gradient to 1 M at pH 5.2. The active fraction from this step was subjected to gel filtration on Sephadex G-100 and finally passed through an Amicon Centriflo membrane CF-25 (cut off point: 25,000 m.w.). The ultrafiltrate was homogeneous by SDS-polyacrylamide gel electrophoresis, had a molecular weight of the order of 23 000 and was capable of suppressing serum gonadotrophin levels in the castrated male rats in as low a dose as 25 microgram/rat.